This invention relates to a method and apparatus for detecting empty or absent packages on a packaging machine system to prevent the dispensing of labels on empty or absent packages. In particular, the method and apparatus comprises a labeling apparatus having proximity sensors mounted thereto to detect empty or absent packages and to communicate such information to the labeling dispenser to prevent the unnecessary dispensing of labels.
In a variety of food and medical packaging operations, a packaging system is utilized .commonly referred to as a horizontal form, fill, and seal packaging machine. These systems index in a start and stop type operation and package an array of products each cycle. And such as operations where a food product is packaged, it is desirable to place labels on the packages. The packager may place the labels manually on the packaging film before the package is filled with product or after the article is packaged. Manual label placement is costly and slow. Thus, packagers have found automated apparatus useful in placing labels on the packaging.
Typically, labels are either (1) placed on packaging film that is then later used to package an article or (2) placed directly on the packaged article. An example of a device that places labels directly on packaging film is described in Harte et al. U.S. Pat. No. 5,725,717. An example of a device that places labels directly on the packaged article is found in Wurz et al., U.S. Pat. No. 5,954,913.
To accelerate the process of placing the labels on the packaging film or the packaged articles, labeling devices are designed to place labels on an array of packages or place several labels across the width of the packaging film. In these devices, the labeling apparatus is perpendicular to the movement of the film or the packaged articles (as illustrated by FIG. 1 and U.S. Pat. No. 5,725,717). Such labeling devices can be designed to apply labels to package arrays varying from a minimum of one row by two tracks, to twenty-four rows by twenty-four tracks, and possibly more.
Labelers designed to place labels on an array of packages will dispense the labels across the index of the packaging machine. The labels are dispensed across a transport unit that extends outward and perpendicular to the packaging machine system. The transport unit spaces the labels appropriately to align the labels with the tracks of the packaging machine system, such that the labels can be placed directly on the packaged articles on the tracks of such system.
To place the labels on these packages, the transport unit has tamping plates that press the labels on the packaged articles. Even when a package is empty, the labeler will place the label on the empty package, thereby wasting labels.
Labeling machines of this type may be mounted upright labeling the top of the package or in an inverted position underneath the packaging machine labeling the bottom of the product. The label machine typically holds the loose labels against a transport unit through vacuum. The transport unit transports and aligns the labels across the row of articles. When a package in the array is empty and the labeling machine is inverted, the labeler would normally attempt to label the entire array but the empty package in the array is generally collapsed and will not accept the label. Then the labels drops back onto the labeling machine which eventually will jam the labeling machine and require the entire line to be stopped to remove loose labels.
Accordingly, there is a need for a method and apparatus that detects when a container is empty or when an article is absent and communicates such information to the labeling apparatus to prevent the labeling apparatus from unnecessarily dispensing labels.
Accordingly, the principle object of the present invention is to provide a method and apparatus for communicating with a labeling machine such that the labeling machine will only dispense and place labels on packaged articles and will not dispense labels onto empty packages or packages missing from the stream of packaged articles.
In the present invention, sensors are positioned in front of the labeling transporter, which positions the labels on the packaged articles. These sensors are preferably positioned directly in front of the transporter over the row of articles preceding the transporter and operate to detect the presence and absence of packaged articles and their content. Thus, if a package is absent from a row or does not contain product, the sensors can alert the labeling machine so that the labeler does not dispense a label for that missing article or empty package.
The present invention utilizes capacitive sensors, such as those sold by Turck, Inc., and is designed primarily for use in connection with articles packaged in packaging film, such as food products. When used with other types of packaging film, capacitive sensors would likely only detect the complete absence of a package and not empty packages. While detecting the absence of a package still provides an advantage to typical array labelers, the full advantages of the present invention are not recognized when used with other types of packaging film. Sensors, however, are designed to detect a wide-variety of items. Thus, one skilled in the art may be easily able to vary the type of sensors used in connection with the present invention to allow the detection of the absence of content packaged in different types of packaging material.